The motor vehicle industry has engaged in a continuous quest to improve fuel consumption and pollution emissions of internal combustion engines that power motor vehicles. One recognized scheme for simultaneously improving fuel consumption and emissions calls for automatically stopping the vehicle's engine when the vehicle is stopped, such as in heavy traffic, at a stop light, during a delivery or quick errand, and the like. When the driver is ready to proceed, the vehicle is restarted. Fuel consumption is reduced because the engine uses no fuel while it is stopped. Emissions are reduced because the engine produces no exhaust while it is stopped.
For a stop/start scheme to be successful, the driver should be required to perform no more than a small part of the scheme. Preferably, such a scheme should be transparent to the normal, conventional operation of a vehicle. Otherwise, complication for the driver increases, and the driver is encouraged to defeat the stop/start scheme. Thus, systems have been proposed to automatically stop then later automatically restart an engine.
Conventional systems have devised generally acceptable schemes for automatically stopping an engine. Typically, one or more sensors may detect whether the engine is idling, whether the vehicle is stopped, or whether the brake is depressed. Based on one or more of these conditions, the engine's ignition may be automatically de-energized or the engine's fuel flow may be automatically disabled to stop the engine. No action beyond the normal operation of the vehicle is required from the driver.
On the other hand, conventional systems have failed to provide an acceptable automatic starting function for a stop/start scheme. Specifically, such systems typically require operation of the vehicle's starter motor in order to restart the engine. The use of the starter motor is particularly undesirable in a stop/start scheme because a vehicle's engine is started many more times than occurs during normal conventional vehicle operation. Conventional vehicle starter motors are far too unreliable for this "heavy-duty" type service. Thus, such conventional starter motors are quickly worn out. While the starter motor and all gears used in starting an engine may be constructed in a more "heavy-duty" fashion, such heavy-duty construction increases vehicle weight and cost. In addition, the increased use of a starter motor places a greater demand on a vehicle's battery. As a result, a larger battery must be used in the vehicle, and this larger battery again increases vehicle weight and costs. The increases in weight harm fuel consumption, and increases in weight and cost together lessen incentives to implement a stop/start scheme to conserve fuel.
Furthermore, the use of a vehicle's starter motor to start an engine tends to make the starting function occur too slowly. For example, a stop/start scheme should monitor various sensors to detect the occurrence of a starting event. Some systems require the driver to actuate a specifically designated starting switch in order to start the engine. Other systems monitor other vehicle sensors, such as brake pedal, ignition switch, gas pedal position, and the like, to automatically actuate a starter motor. In either situation, at least a couple of seconds must transpire after the occurrence of a starting event before the vehicle may proceed. This duration is undesirably long because it forces drivers to operate their vehicles in an unconventional manner.